Issue 10871. Fix for analyzing file without absolute path

pkg/analyzer_experimental/lib/src/analyzer_impl.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer_impl;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'generated/java_io.dart';
@@ skipping 53 matching lines @@
         status = status.max(severity);
       }
     }
     return status;
   }
 
   void prepareAnalysisContext(JavaFile sourceFile) {
     List<UriResolver> resolvers = [new DartUriResolver(sdk), new FileUriResolver()];
     // may be add package resolver
     {
-      var packageDirectory = getPackageDirectoryFor(sourceFile);
+      JavaFile packageDirectory;
+      if (options.packageRootPath != null) {
+        packageDirectory = new JavaFile(options.packageRootPath);
+      } else {
+        packageDirectory = getPackageDirectoryFor(sourceFile);
+      }
       if (packageDirectory != null) {
         resolvers.add(new PackageUriResolver([packageDirectory]));
       }
     }
     sourceFactory = new SourceFactory.con1(contentCache, resolvers);
     context = AnalysisEngine.instance.createAnalysisContext();
     context.sourceFactory = sourceFactory;
   }
 
   /// Fills [sources].
@@ skipping 46 matching lines @@
 
   /// Fills [errorInfos].
   void prepareErrors() {
     for (Source source in sources) {
       var sourceErrors = context.getErrors(source);
       errorInfos.add(sourceErrors);
     }
   }
 
   static JavaFile getPackageDirectoryFor(JavaFile sourceFile) {
-    JavaFile sourceFolder = sourceFile.getParentFile();
-    JavaFile packagesFolder = new JavaFile.relative(sourceFolder, "packages");
-    if (packagesFolder.exists()) {
-      return packagesFolder;
+    // we are going to ask parent file, so get absolute path
+    sourceFile = sourceFile.getAbsoluteFile();
+    // look in the containing directories
+    JavaFile dir = sourceFile.getParentFile();
+    while (dir != null) {
+      JavaFile packagesDir = new JavaFile.relative(dir, "packages");
+      if (packagesDir.exists()) {
+        return packagesDir;
+      }
+      dir = dir.getParentFile();
     }
+    // not found
     return null;
   }
 }